Miniaturized Wireless Ultrasound Energy Transfer System for Powering a Bio-Implantable Medical Device

ABSTRACT

A system for providing energy to a bio-implantable medical device includes an acoustic energy delivery device and a bio-implantable electroacoustical energy converter. The acoustic energy delivery device generates acoustic energy with a multi-dimensional array of transmitting electroacoustical transducers. The acoustic energy is received by one or more receiving electroacoustical transducers in the bio-implantable electroacoustical energy converter. The receiving electroacoustical transducers convert the acoustic energy to electrical energy to power the bio-implantable medical device directly or indirectly. An external alignment system provides lateral and/or angular positioning of an ultrasound energy transmitter over an ultrasound energy receiver. The acoustic energy transmitter alignment system comprises either or both x-y-z plus angular positioning components, and/or a substantially multi-dimensional array of transmitters plus position sensors in both the transmitter and receiver units.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.62/332,100, titled “Miniaturized Wireless Ultrasound Energy TransferSource Using a Combination of Positioning and Alignment Methods,” filedon May 5, 2016, which is hereby incorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under grant number R43EB019225 awarded by the National Institutes of Health. The governmenthas certain rights in the invention.

TECHNICAL FIELD

The present application relates to the ultrasonic transmission ofelectrical power between electronic devices.

BACKGROUND

Implantable electronic medical devices represent a large and growingcommercial market. The lifetime of implanted electronic medical devicesis typically limited by the life of their primary (non-rechargeable)batteries. Replacing them requires a costly procedure to remove thepreviously implanted medical device and replace it with another thatcontains new primary batteries. The surgery also introduces the risk ofinfection.

Rechargeable batteries carry the promise of a longer overall lifetimefor many applications, reducing the number of such procedures, hence thecosts in money and trauma to the patient. The lifetime of a permanentimplanted battery, perhaps 7-10 years, may be adequate for someapplications. But in pain neurostimulators and combinationpacemakers-defibrillators, the batteries are discharged faster,sometimes depleting their batteries in 1-3 years. Moreover children andyoung adults who get these implants will face many more permanentbattery replacements, so even incremental increases in implant lifetimewill be useful.

U.S. Pat. No. 8,082,041 (Radziemski) (incorporated herein by reference)describes an ultrasound system suitable for providing power to implanteddevices such as pacemakers, defibrillators, and neurostimulators, andsensors primarily to recharge implanted batteries, however with thecapability of also delivering power directly to an application.Batteries for such low power devices may be charged for periods ofminutes to hours at rates that vary from once per day to once per weekor month, or even less frequently. The aforesaid patent also contains adescription of medical ultrasound power transmission.

Several methods for providing data for alignment of transmitter andreceiver are taught in Radziemski. Typically, in those prior systems thealignment would be performed manually, by physically adjusting theorientation of the external transmitter unit in response to the dataprovided.

U.S. Pat. No. 8,974,366 (Radziemski and Makin) (incorporated herein byreference), discloses a full-time energy delivery ultrasound method to astorage device or directly to an application, plus a full-timenon-mechanical alignment system.

Willis (US2008/0294208), incorporated herein by reference, teaches atwo-dimensional ultrasound array to scan and search for a receiverlocated in or on the heart, to wirelessly provide pacing level voltagesto the heart. Willis (U.S. Pat. No. 8,364,276), incorporated herein byreference, estimates the energy per pacing pulse provided as 0.17 microJoules in a 0.5 millisecond pulse. Assuming a pulse rate of 60 persecond, this converts to an average power of 0.17 micro Watts.

SUMMARY

Example embodiments described herein have innovative features, no singleone of which is indispensable or solely responsible for their desirableattributes. The following description and drawings set forth certainillustrative implementations of the invention in detail, which areindicative of several exemplary ways in which the various principles ofthe invention may be carried out. The illustrative examples, however,are not exhaustive of the many possible embodiments of the invention.Without limiting the scope of the claims, some of the advantageousfeatures will now be summarized. Other objects, advantages and novelfeatures of the invention will be set forth in the following detaileddescription of the invention when considered in conjunction with thedrawings, which are intended to illustrate, not limit, the invention.

An aspect of the invention is directed to a system for providing energyto a bio-implantable medical device, the system comprising: an acousticenergy delivery device configured to be secured to a patient's skin andapposed superficial tissue and a bio-implantable electroacousticalenergy converter configured to be electrically coupled to thebio-implantable medical device, the bio-implantable electroacousticalenergy converter coupled to the patient's skin tissue. The acousticenergy delivery device comprises a delivery device housing; amulti-dimensional array of transmitting electroacoustical transducersdisposed on or in the delivery device housing, the multi-dimensionalarray of transmitting electroacoustical transducers arranged in asubstantially regular two-dimensional geometric shape; a signalgenerator and power output board disposed in the delivery devicehousing, the signal generator in electrical communication with themulti-dimensional array of transmitting electroacoustical transducers; amicroprocessor-based controller disposed in the delivery device housing,the microprocessor-based controller in electrical communication with thesignal generator and the multi-dimensional array of transmittingelectroacoustical transducers; and a battery disposed in the deliverydevice housing, the battery electrically coupled to themulti-dimensional array of transmitting electroacoustical transducers,the signal generator and power output board, and themicroprocessor-based controller. The bio-implantable electroacousticalenergy converter comprises a converter device housing; one or morereceiving electroacoustical transducers disposed on or in the converterdevice housing, the one or more receiving electroacoustical transducersconfigured to convert acoustic energy received from the acoustic energydelivery device into converted electrical energy; and an energyrectification and storage device disposed in the converter devicehousing, the energy storage device in electrical communication with theone or more receiving electroacoustical transducers to store at least aportion of the converted electrical energy.

In one or more embodiments, the bio-implantable electroacoustical energyconverter further comprises a microcontroller disposed in the converterdevice housing. In one or more embodiments, the system further comprisesa wireless feedback loop between the bio-implantable electroacousticalenergy converter and the acoustic energy delivery device. In one or moreembodiments, the microcontroller is configured or programmed to modulatean impedance of the one or more receiving electroacoustical transducersto form the wireless feedback loop. In one or more embodiments, themicrocontroller is configured or programmed to modulate an electricalload on a charging circuit that electrically couples the one or morereceiving electroacoustical transducers to the energy storage device. Inone or more embodiments, the acoustic energy delivery device furthercomprises a first RF antenna and the bio-implantable electroacousticalenergy converter further comprises a second RF antenna, the wirelessfeedback looped formed by RF communication between the first and secondRF antennas.

In one or more embodiments, the system further comprises a programmableexternal controller in electrical communication with the acoustic energydelivery device. In one or more embodiments, the microprocessor-basedcontroller is configured or programmed to adjust a relative phase ofinput signals generated by the signal generator to steer a beam of theultrasonic energy. In one or more embodiments, the system furthercomprises first magnets disposed on the delivery device housing andsecond magnets disposed on the skin tissue or on the converter devicehousing, the first magnets having an opposite polarity to the secondmagnets to magnetically retain an alignment of the acoustic energydelivery device and the bio-implantable electroacoustical energyconverter. In one or more embodiments, the system further comprisesx-y-z and angular alignment mechanical devices to optimize alignment oftransmitter transducer and receiver transducer faces. In one or moreembodiments, the system further comprises an acoustically transparentadhesive to secure the acoustic energy delivery device to the patient'sskin. In one or more embodiments, the acoustic energy delivery deviceand the bio-implantable electroacoustical energy converter each comprisea gyroscope and an accelerometer. In one or more embodiments, themicroprocessor-based controller receives angular position andtranslational position data from the gyroscope and the accelerometer inthe acoustic energy delivery device and from the gyroscope and theaccelerometer in the bio-implantable electroacoustical energy converter,the microprocessor-based controller configured or programmed to adjust arelative phase of input signals generated by the signal generator tosteer a beam of the ultrasonic energy according to a relative angularposition and a relative translational position of the bio-implantableelectroacoustical energy converter with respect to the acoustic energydelivery device. In one or more embodiments, the system furthercomprises a dry acoustic coupling between the multi-dimensional array oftransmitting electroacoustical transducers and the patient's skin. Inone or more embodiments, the dry acoustic coupling comprisespolyurethane, silicone, natural oils, fatty-acids, polyacrylamide, alipophilic material, or a hydrophilic material. In one or moreembodiments, the dry acoustic coupling includes a dynamic coupling tooptimize impedance matching of the transmitting electroacousticaltransducers to the dry coupling material.

Another aspect of the invention is directed to a method for providingpower to bio-implanted medical device, the method comprising: securingan acoustic energy delivery device on a subject's skin tissue proximalto the bio-implanted medical device; generating acoustic energy with amulti-dimensional array of transmitting electroacoustical transducers onor in the acoustic energy delivery device; receiving the acoustic energywith one or more receiving electroacoustical transducers on or in abio-implanted electroacoustical energy converter that is electricallycoupled to the bio-implanted medical device; with the one or morereceiving electroacoustical transducers, converting the acoustic energyinto electrical energy; and providing the electric energy to thebio-implanted medical device.

In one or more embodiments, the method further comprises providing awireless feedback signal from the bio-implanted electroacoustical energyconverter to the acoustic energy delivery device, the wireless feedbacksignal corresponding to a magnitude of the acoustic energy received bythe bio-implanted electroacoustical energy converter. In one or moreembodiments, the acoustic energy delivery device adjusts an angular orlateral position of a beam of the acoustic energy based on the wirelessfeedback signal. In one or more embodiments, the acoustic energydelivery device adjusts a frequency of the acoustic energy based on thewireless feedback signal. In one or more embodiments, the feedbacksignal is provided by varying an acoustic impedance of the one or morereceiving electroacoustical transducers. In one or more embodiments, themethod further comprises adjusting a relative phase of input signals tothe multi-dimensional array of transmitting electroacousticaltransducers to steer a beam of the acoustic energy based on the wirelessfeedback signal.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the present invention will be seenfrom the following detailed description and in connection with theaccompanying drawings where like numerals depict like parts.

FIG. 1A is a schematic diagram of a USer system according to anembodiment.

FIG. 1B illustrates the components of the USer system and their possiblelocations on the body or torso of a patient.

FIG. 2 shows two novel stages of miniaturization of the USer system withdecreasing circuit size.

FIG. 3 illustrates the shrinking of the volume of the implant assemblyby comparing two designs and of the implant assembly.

FIG. 4A illustrates a top view and a cross-sectional view of a noveltransmitter apparatus that has these alignment mechanisms.

FIG. 4B illustrates an alternative embodiment for placing a transmitterapparatus securely over the receiver.

FIG. 5 illustrates an example of a phased transducer array and itsability direct or steer the generated acoustic (e.g., ultrasound)energy.

FIG. 6 is a schematic illustration of certain components in a systemhaving a transmitter apparatus and an implanted receiver apparatusaccording to one or more embodiments.

FIG. 7 illustrates the details of driving an array to produce beamsteering and power transmission from a transmitter apparatus to animplantable receiver apparatus according to one or more embodiments.

FIG. 8 is an exemplary model-based calculation result for an ultrasoundfrequency of 1 MHz and 25 mm diameter transducers.

FIG. 9 is a flow chart that illustrates an exemplary feedback methodused to optimize the position of each axis of the lateral and angularalignments, and the frequency from the signal generator.

FIGS. 10A and 10B illustrate examples of a dry coupling medium.

FIG. 11 illustrates a schematic of two-way communication usingultrasound.

FIG. 12 is a flow chart of a method for providing power to bio-implantedmedical device.

DETAILED DESCRIPTION

The present invention relates to systems for powering implanted medicaldevices directly or via stored energy. The invention has particularutility for systems for powering implanted medical devices requiringperiodic delivery of electrical power for implanted applications such asa variety of neurostimulators or sensors. These will be described inconnection with such utility, although other utilities are contemplated.The following describes several system and method embodiments of thepresent invention, including various preferred embodiments thereof. Itshould be understood that the present examples are provided by way ofillustration of the invention, and are not intended to be exhaustive orlimiting. Those skilled in the art will appreciate further aspects orequivalent implementations of the invention upon review of the presentdisclosure, all of which are intended to be contemplated by and includedin this disclosure.

In an aspect, conveniently retaining alignment between transmitter andreceiver can be a critical feature of power delivery to an implant,whether by ultrasonic or electromagnetic means. In a unique aspect,ultrasound power delivery can mitigate the effects of lateral andangular misalignment by non-mechanical electronic means via atwo-dimensional array of piezoelectric elements, leading to a dynamic,hands-off, real-time, self-aligning system that does not require patientintervention. Also, the ultrasound beam, in the near field may notdiverge significantly, hence losses due to depth of the implant areminimal. Both of these advantages accrue to ultrasound because of itswave nature, and the fact that for power transfer, the ultrasoundwavelength at useful frequencies is much smaller than the dimensions ofthe ultrasound transducers. In electromagnetic power delivery theconverse is true, discouraging the use of non-mechanical alignment.

The present disclosure refers to an Ultrasound Electrical power deliverysystem (“USer”) that, in some embodiments, transmits 10⁶ times morepower than described in the aforementioned prior art, continuously orwith duty cycles of 30% up to 95%.

FIG. 1A is a schematic diagram of a USer system according to anembodiment. The USer system includes an external controller 100 inelectrical communication with a transmitter assembly 120 disposed on oradjacent to the subject's skin and apposed superficial tissue 130. Infuture reference to the “skin and apposed superficial tissue” withinthis specification, for simplicity, this tissue will be described as“skin.” The transmitter assembly 120 includes one or more transmittingultrasonic transducer elements to transmit ultrasound energytranscutaneously through tissue or skin 130 to an implant assembly 140.The implant assembly 140 includes one or more receiving ultrasonictransducer elements that receive the ultrasound energy and convert itinto electrical energy to power an implanted medical device. Theimplanted medical device can be powered directly from the convertedelectrical energy or indirectly, for example via an energy storagedevice included in the implant assembly 140. Examples of such an energystorage device include a rechargeable battery, a capacitor, or otherenergy storage device.

The external controller 100 controls the level of input power andfrequency of the ultrasound transmitter generated by transmitterassembly 120, bidirectional communication (e.g., between the externalcontroller 100 and the transmitter assembly 120 and between thetransmitter assembly 120 and the implant assembly 140), and if needed,the level of external cooling. The external controller 100 can alsocontrol an alignment feedback loop and/or an orientation optimizationalgorithm, as further discussed below. The transmitter assembly 120 andthe implant assembly 140 each include an RF antenna 150 forbidirectional wireless RF communication 110 between the transmitterassembly 120 and the implant assembly 140. For example, the wireless RFcommunication 101 can be over the 405 MHz medical band, such as with aZarlink or other brand of medical-band RF communication system. Inaddition or in the alternative, bidirectional communication can beaccomplished using the ultrasound energy (e.g., as discussed below).

The external controller 100 can be operated in two modes, manually andautomatically, the latter via a feedback loop made possible by thewireless bidirectional communication between the transmitter assembly120 and the implant assembly 140, which can have external and internalcomponents. The output of the external controller 100 is connected tothe transmitting assembly 120, which is disposed adjacent to the skintissue 130 of the subject. In some embodiments, signals or datacorresponding to the acoustic energy or power received by the implantassembly 140 is communicated to the transmitter assembly 120 using thefeedback loop.

The transmitting ultrasonic transducer elements transmit acoustic energyvia sine waves, square waves, triangular waves or an arbitraryrepetitive shape. A cooling system may be deployed on or proximal to thetransmitter assembly 120. During in vivo tests through 1-2 cm of tissueexternal cooling has been observed to penetrate the dermis, cooling theintervening tissue and the implant as well.

After penetrating the epidermis, dermis, and possibly fat and musclelayers, the ultrasound is incident on a biocompatible implantedcontainer or housing which has the receiving ultrasonic transducerelements on or against the inside of the front face, and other elementspackaged within it. The receiving ultrasonic transducer elementsconverts the ultrasonic to electrical energy, which is used to directlyor indirectly power an implanted medical device. The implantable medicaldevice and the implant assembly 140 can be combined in the same deviceor they can be separate devices that are electrically coupled.

FIG. 1B illustrates the components of the USer system and their possiblelocations on the body or torso of a patient 10. The battery-poweredcontroller and power supply 100 could be attached to a belt at waistlevel or as shown on the right of the torso. The transmitter assembly120, electrically coupled to controller 100, resides up against the skintissue 130 of the patient 10. An ultrasound beam 120 then relays powerto the implant assembly 140, which is directly below (or across from)the transmitter assembly 120. The transmitting assembly 120 and implantassembly 140 may be positioned in various locations, on the upper chestbelow the clavicle, or lower on the belly, or to one side or slightly orcompletely toward the rear of the patient 10.

Implanted devices are becoming smaller and smaller in order to satisfyconsumer demand and improve ease of implantation. Hence it is preferablethat the circuitry and receiver element take up as small a volume aspossible. FIG. 2 shows two novel stages 201 and 202 of miniaturizationof the USer with decreasing circuit size. Some technological aspectsthat may be employed in one or more embodiments of the USer include: (a)surface-mount technology (SMT) to reduce printed circuit board (PCB) 205size; (b) SMT with a double-sided PCB to further reduce areal andvolumetric size; (c) bare dies instead of packaged devices and use wiredie-bonding for interconnects to further reduce areal and volumetricsize/weight; (d) multi-layer PCBs to route interconnections betweencomponents to further reduce PCB areal and volumetric size/weight;ability to accommodate wireless communications whether by RF orultrasound.

Stage 2 202 achieves further novel miniaturization through use of amulti-layer printed circuit board (PCB) and smaller semiconductor devicepackages to develop a pre-production prototype. Wirelesstelecommunication compliant with the Medical Device Radio-CommunicationsService (MedRadio) can be implemented in the design of the USer.Wireless telecommunication can also comply with the internationalstandard IEEE 802.15.6 for Wireless Body Area Network (WBAN) forreliability and security. To reduce the size, a total volume of thecircuit may be kept under 0.8 cm³, which is achieved in two stages. Inthe first stage 201 a PCB in surface-mount technology (SMT) is made withcomponents spread out sufficiently to allow for modifications in thecircuit having a volume of approximately 2.2 cm³. In the second stage202 the circuit is assembled in the highest practical density withdouble-sided component population of the PCB and wire-bonded bare diechips having an estimated volume of 0.8 cm³. Again, these figures andexamples are merely illustrative of the aspects of the present inventionand are not intended to be limiting of it.

A substantial decrease in total circuit volume can be achieved by usingbare die devices instead of packaged semiconductors. Each stage 201, 202includes a PCB 205 on which a microcontroller (MCU), a voltage regulator(VR), current-to-voltage converters (IV), a Zener diode (ZD), acapacitor (Cap), bridge rectifiers (BR), a motion sensor (MS), aninductor (L), a charging circuit (CC), and a transceiver (RF) aredisposed.

The stages 201, 202 of circuits on the PCBs 205 were drawn using theEAGLE computer-aided design tool (available from Autodesk, Inc.) to have0.8 mm thin multi-layer boards made. After all connections were made,the circuit was cast in insulating epoxy to protect the delicatehardware and create a rugged module.

FIG. 3 illustrates the shrinking of the volume of the implant assemblyby comparing two designs 340A and 340B of implant assembly 140. Thevolume reduction between designs 340A and 340B was more than a factor of10. The newer, miniaturized implant assembly design container profile310 is illustrated in design 340A on the left-hand side of FIG. 3, withelectronics 311. Design 300B includes a two-piece puck-sized containerwith top 301 and bottom 303, inside of which is a much larger circuitboard 302 containing the electronics.

The controller and RF transceiver chips in implant assembly 140 canprovide ultra-low power consumption by offering a sleep-mode wherecurrent draw drops into the nano-Amp range to maximize battery life. Thechips can be awakened to full functionality in less than 100microseconds. Having an on-board microcontroller offers greatflexibility for system control through the programming of the firmware.

The transmitter unit of the ultrasound power delivery system can presentthe transmitter transducer to the skin with lateral, angular, and/oraxial alignment mechanisms to optimize transmitter-receiver powertransfer. FIG. 4A illustrates a top view 401 and a cross-sectional view402 (through line A-A) of a novel transmitter apparatus 400 that hasthese alignment mechanisms, an earlier version of which has been used inanimal tests.

The transmitter apparatus 400 includes lateral, angular, and axialalignment mechanisms attached to a cylindrical clamp 406. Thetransmitter apparatus 400 including transmitting transducers 402 areheld in a cylindrical clamp 406 in which the transmitter apparatus 400can be adjusted in the Z-axis by adjusting thumb screws 408, to createthe optimal pressure on the subject's tissue. The clamp 406 is mountedwith a pivot 407 to a frame 403. Frame 403 can be formed out of plastic(e.g., acrylic), aluminum, another material, or a combination of any ofthe foregoing. The three thumb screws 408 perform angular adjustment.The frame 403 is attached to an X-Y linear positioner 404, which allowsfor lateral adjustment of the transducer along the X- and Y-axes (in thex-y plane parallel to the skin surface of the subject). These axes arealso user-adjustable in situ by thumb screws 4041. The X-Y linearpositioner 404 is mounted on a frame 414 that matches the implant holderwith magnets 405 of opposite polarity at the same positions on animplantable receiver unit collar. Frame 414 can be formed out of plastic(e.g., acrylic), aluminum, another material, or a combination of any ofthe foregoing. A large cross-shaped cutout 413 in the frame 414accommodates a reasonable range of motion in the lateral-, and angularaxes. The magnets 405 on the frame 414 and on the correspondingimplantable receiver collar unit provide magnetic coupling and alignmentbetween transmitter 400 and receiver units. For example, the magnets 405on the frame 414 and on the implantable receiver collar unit areattracted to one another (due to opposite polarity). Such attractivemagnetic force allows the transmitter unit 400 to maintain alignmentwith the receiver unit.

FIG. 4A illustrates the top of the transmitter apparatus 400 includingthe frame 414 to hold the transmitter apparatus 400 and the alignmentmagnets 405. The magnets 405 in the frame 414 can be arranged withalternating polarities (i.e., adjacent magnets 405 along thecircumference of the frame 414 can have opposite polarities) to create afield line pattern that results in more attractive force compared to apattern that has same polarities. The magnets 405 can protrude to acertain extent (e.g., 1-5 mm) from the frame 414 to bring their polescloser together for a more attractive magnetic force while maintainingthe same distance between sending and receiving transducers elsewhere.Several geometries were tested. In one embodiment, the implantablereceiver unit collar was slightly tapered to permit the magnets 405 tofit snugly into their holes. The magnets 405 may have a favorablegeometry to produce the highest force-to-size/weight ratio. The magnets405 may also be electromagnets whose strength can be varied.

The aforementioned magnetic method can be used over distances throughwhich the transmitter and receiver unit magnets can act on one another,probably no more than a few (e.g., 0-3) centimeters. A more flexiblenon-magnetic method would be to affix the transmitter unit securely toone location, on the skin, directly over the receiver unit.

FIG. 4B shows an alternative embodiment for placing a transmitterapparatus 420 securely over the receiver. An adhesive 421 is disposed onthe bottom of the transmitter 420 on either side of the transmittingtransducers 422. The adhesive 421 can be disposed on a biocompatible andacoustically transparent film, which is attached to the bottom of thetransmitter apparatus 420. For example, the adhesive can cause thetransmitter apparatus 420 to adhere and stay in place for four hours ormore. Fabrico Inc. makes an example of this kind of biocompatible- andacoustically-transparent film, which for this application may includepressure-sensitive adhesive tapes for high strength medical bonds andgentle adhesion, precision die-cut adhesives, and select tape- andfilm-based adhesives for a variety of medical applications, all of whichcould be used in securing the transmitter unit 420 to the skin.

In addition or in the alternative to using adhesive 421, the transmitterapparatus 420 can be secured with snaps such as those used when securingelectrodes to the body for electrocardiograms. The female components onthe bottom of the transmitter unit would be aligned with the malecomponents on the skin (or vice versa), the latter being placed so as toposition the transmitter approximately above the receiver. As is wellknown from the electrocardiogram application, this combination can keepa unit secured to the skin for up to 24 hours or even for days. Inaddition to the alternative using adhesive 421, one may combine themagnetic and adhesive methods. In this case, the magnets 405 in frame414 can be paired with magnets of opposite polarity placed on top of theskin inserted into adhesive pockets which would replace the male snapcomponents.

The embodiments described with respect to FIG. 4B have the advantage ofsecuring the transmitter unit with a much lighter material and frame,thereby making that unit lighter and easier to manipulate.

However a method of fine tuning the alignment both in translation andangularly is still required to achieve maximum efficiency of powertransfer. FIG. 4B illustrates such a method, which itself has the virtueof being much lighter and easily manipulated than the one of FIG. 4A,which uses precision micrometers which unfortunately are heavy.

The transmitter apparatus 420 also includes a cover 427, a wire 426connected to a power source (e.g., a battery, such as a battery inexternal controller 100). The transmitter apparatus 420 further includesstepper motors 423, 424, which can rotate and/or translate thetransmitting transducers 422 (e.g., with respect to the X-Y plane), forexample in response to the above-described feedback loop and/ordetection of reflected power. The feedback can be processed by amicrocontroller incorporated in the electronics module 425. An exampleof this feedback loop is described in U.S. Pat. No. 8,974,366 (e.g., incolumn 15), discussed above.

In addition or in the alternative to the lightweight alignment systemsof FIGS. 4A and 4B, phased ultrasound transducer arrays can be used todirect or steer the beam to the target receiver implant assembly.Ultrasound energy is most efficiently transferred when transmitting andreceiving piezo transducers are properly aligned. Movements of thepatient misalign the transducers, resulting in less than optimal energytransfer. Retaining alignment manually is stressful for the patient.There are two geometrical issues affecting alignment of a transmitterover a receiver in both the electromagnetic and ultrasound methods. Thefirst is one- or two-dimensional lateral translation (e.g., in the X-Yplane parallel to the subject's skin) over the implant, and the secondis one- or two-dimensional angular misalignment between the transmitterand receiver. With ultrasound, the use of a one- or two-dimensionaltransducer arrays in the transmitter apparatus enables compensation foreither or both of these misalignments.

FIG. 5 illustrates an example of a phased transducer array and itsability direct or steer the generated acoustic (e.g., ultrasound)energy. The one-dimensional array 500 illustrated in FIG. 5 is a seriesof narrow piezo elements 510 in a row. When the same phase difference ortime delay is introduced between each element 510, the beam 520 isdeflected. A non-uniform phase difference can be used to generate aconverging or diverging beam. A single array in the one- ortwo-dimensional transmitter may suffice, or a second one- ortwo-dimensional array in the receiver may be used to enhance thealignment. The degree of offset can be established by feedback from theimplanted receiver signal and reduced power transfer (e.g., communicatedthrough the feedback loop described above). Additionally themisalignment can be gauged by the magnitude of the back reflectedacoustic signal from the receiver surface.

Other materials may be used either in single element 510 or array 500 oftransducers, such as magnetostrictive materials or capacitivemicrofabricated ultrasonic transducers (CMUTs). In one embodiment, apiezoelectric disk comprised of a ceramic matrix in which are embeddedcrystals of Lead-Zirconium-Titanate (PZT), also called a composite, canbe the basis of one or more transducer elements 510. Other materialssuch as crystalline Lead-Magnesium-Niobate in Lead-Titanate (PMN-PT) mayalso be used.

Ultrasonic transducers micro-machined with semiconductor equipment offerthe promise of size, weight, and cost reduction. A promising type ofdevice is called a pMUT (piezoelectric micro-machined ultrasoundtransducer). These offer the potential to operate at much lower transmitvoltages than transducers which rely on bulk piezoelectric materialarea. Transducers of other shapes, such as curved non-planar geometriescan also be used to modify the directivity of transmitter ultrasoundbeam and/or receiver cone of beam acceptance.

Positioning electronics combined with ultrasound arrays can be used tooptimize power delivery and generate hands-off, non-mechanicalalignment. In an example, a pair of 9-axes angular and lateral positiondetectors (chips), such as gyroscopes and accelerometers, are placed inthe implanted receiver as well as in the transmitted apparatus.Streaming orientation data from both sensors are compared in real-timeto determine the translational and angular position of the piezoreceiver with respect to the piezo transmitter. Once so determined, thephase difference corresponding to the displacements is entered into thebeam-control software (e.g., in external controller 100) to position thebeam in its optimum location. Slight dithering about that position maybe used to confirm or further optimize the power transfer, because theintervening tissue medium can deflect the ultrasound beam slightly, andused for rapid adjustment of the ultrasonic wavefront to maintainoptimal alignment.

FIG. 6 is a schematic illustration of certain components in a system 600having a transmitter apparatus 620 and an implanted receiver apparatus640 according to one or more embodiments. Transmitter apparatus 620drives ultrasound piezo transmitters 626 which provides the ultrasoundbeam incident on the receiver 642. Beam direction is dynamicallycontrolled in real-time by inputs from the sensors placed in the implantand the transmitter unit for optimal energy transfer and communication.Transmitter apparatus 620 includes a piezo driver 621, a signalgenerator 622, a wireless module 623, a battery pack 624, amicrocontroller and power output board 625, and ultrasound piezotransmitters 626 attached by a flexible cable 628. The microcontrollerboard 625 includes a microcontroller and one or more position and/ororientation sensor readout(s). In addition, the microcontroller onmicrocontroller board 625 can control an accelerometer and/or amagnetometer in a positioning chip 627 in the transmitter 626. Anexample of a microcontroller board 625 of this type is the MPU-9250 chipfrom InvenSense, Inc. providing a minuscule package of only 3 mm×3 mm×1mm (length×width×height). The microcontroller board 625 may be embeddedin transmitter apparatus 620 by a flexible cable 629. In addition or inthe alternative, a second microcontroller board can be incorporated intothe receiver electronics 641. The second microcontroller board includesa microcontroller that can control an accelerometer and/or amagnetometer in a positioning chip 627 in the receiver apparatus 640.

The accelerometer and/or the magnetometer can provide respectivemeasurements (i.e., acceleration and magnetism, respectively) in up to 3axes, for example, in the X-, Y-, and Z-directions in a Cartesiancoordinate system. In some embodiments, the high-integratedmicrocontroller board 625 also includes signal conditioning circuits611, analog-to-digital converters, a digital motion processor, and/or aserial interface 629 for an inter-integrated circuit (I2C) bus tocommunicate with the microcontroller. Note that microcontroller board625 may be coupled to other circuit and system components as would bereasonably implemented by those skilled in the art and depending on theneed at hand. For example, the board and/or processing circuit(s) can beintegrated or separate from said other circuits and said system invarious embodiments.

The combined data of these 9 axes (from the 3-axes accelerometer and the3-axes magnetometer (also called a positioning chip)) make it possibleto accurately determine the absolute and relative angular and lateralpositions of the ultrasound piezo transmitters 626 and the ultrasoundpiezo receiver 642. Both transmitter 626 and receiver unit 640 wouldhave one of the positioning chips 627 in it. These data can be input tothe phased array of ultrasound piezo transmitters 626 to control beamsteering and maintain optimal ultrasound energy transfer andbidirectional communication. The fast-responding electronics (sensorreadout, signal processing, algorithm processing and actuation) inmicrocontroller board 625 have time constants much shorter than thephysical movements of transmitter 626, subject, and implantable receiver640, to effectively track optimal operating conditions with minimaldwell time in less-than-optimal operating conditions.

The implanted receiver apparatus 640 includes electronics 641 which caninclude a microprocessor, an ultrasound receiving transducer(s) 642, anda positioning chip 627. The ultrasound piezo receiver transducer(s) 642is/are bonded to the face of the receiver apparatus. The positioningmicrochip 627 is disposed very close (e.g., less than 5 mm from) to thepiezo element 642 so that it can provide accurate spatial positioninformation.

The receiver circuit rectifies the 1 MHz sinusoidal signal from thereceiver transducer. The circuit drives a charging chip, and conditionsthe received power to charge the secondary battery in a stable manner.In addition, functional and safety parameters, such as receiverimpedance, multipoint temperature measurements as well as chargingcurrent and various tapped voltages within the charging circuit areconstantly monitored within the Receiver apparatus 640. The Receiverapparatus 640 constantly (or frequently or nearly constantly)communicates with the transmitter apparatus 620 located outside thebody. The aim of the circuit within the receiver apparatus 640 is tomaintain an adequate charge in the secondary battery in order that theimplant device can operate in a reliable and safe manner.

The controller 100 and/or transmitter apparatus 620 will have a simplerechargeable cell phone battery pack having adequate energy storage anda total volume half that of a standard cigarette pack. That stores ampleenergy to a) generate the 1 MHz drive frequency for the ultrasonictransducer, b) for ancillary electronics, and c) enough for a fewcharging cycles. The electronics include control and displaycapabilities as well as circuitry communicating with the implant and,during research or to download performance characteristics periodically,a laptop computer.

In one embodiment, the traditional USB cable will be replaced with awireless Bluetooth dongle or internal (or external) Bluetooth antenna. Auser control panel with digital display for key charging parameters isattached to the driver unit.

The controller 100 has several important functions. It may also be usedto monitor and change the frequency of the ultrasound source. Typicallythe range of changes are approximately 10% of the resonant frequency,and this is achieved via a variable frequency oscillator or asynthesized signal generator. The frequency can be set manually with aninput command, or can be placed under the control of a frequencyfeedback loop.

Two other controller functions may include monitoring and aligning thetransmitter and receiver faces non-mechanically, and energy managementto regulate the heat removal needed for safe operation.

In an embodiment, the controller includes the electronics which enablereception of communications from the implant on a radio-frequencymedical communication band, or acoustically from the transmitter unit.These comprise receiving values of temperatures being monitored invarious implant locations, monitoring the efficiency of powerconversion, and monitoring transmitter and receiver unit alignment. Inone embodiment, a hybrid National Instruments Signal Express plus C++code collects and stores the data automatically and continuously for upto 10 or even 20 parameters, both for patient information on a userinterface and for periodic diagnostic downloading. The latter allows avariety of charts, comparisons, and figures of merit to be recorded andanalyzed, to monitor the performance of the system.

Software compares the temperature readings with a preset regime of safetemperatures and, if necessary, sends a warning to a user interface,similar to a smart phone, which allows the patient to monitor powerefficiency and control charging. The user interface communicates withthe controller using a wireless protocol, such as Bluetooth, Wi-Fi, orother advanced method.

FIG. 7 illustrates the details of driving an array to produce beamsteering and power transmission from transmitter apparatus 720 toimplantable receiver apparatus 740 according to one or more embodiments.The transmitting transducer 730 is comprised of an 8×8 array of 3 mmsquare piezoelectric elements 731. The multi-element 731 matrix intransmitting transducer 730 can be used to reduce or eliminatetransducer misalignment, which can occur on two axes. Additionally, thetransmitted beam can be focused by using variable phase algorithms wellknown to those experienced in the field.

The transmitting transducer 730 is controlled by FPGA 710 such as oneproduced by Altera or Xilinx. Development PCBs containing FPGAs and aninterface to a PC are available inexpensively from vendors such as OpalKelly Inc. In an aspect, FPGA 710 has several functions, including thegeneration of 64 logic outputs at 1 MHz, with signals of correct phasesto maximize power transfer, for example to present a flat phase front tothe receiving transducer 740, regardless of the relative orientation ofthe transmitting transducer 730 and the receiving transducers 740. Theseoutputs are fed to a plurality of pulser ICs 720. An example of asuitable commercial pulser IC is the HV7350, an 8-channel design byMicrochip Technology Inc. These pulser ICs 720 provide the levelshifting and high voltage output stage suitable for driving the array ofpiezoelectric elements 731.

In addition, FPGA 710 controls timing for the start and stop ofcharging, and senses the temperature at the array surface using athermocouple to discontinue operation if a fault condition occurs.Software for the FPGA is developed on a standard PC (e.g., developmentPC 700) and transferred to the FPGA's circuit board using a USBconnection. The program for the FPGA 710 is stored in a flash memorydevice 705, whose contents (the “bit-file”) are loaded into the FPGA 710when power is first applied to the circuit. The FPGA 710 is incommunication with an external controller (e.g., external controller100), which provides commands and instructions for operation.

Another embodiment may incorporate a closed-loop system in which thereceiver reports to the transmitter data on power transfer and alignmenterrors using Bluetooth, as indicated in FIG. 7. The FPGA 710 uses thisdata to alter the phases of its outputs, so that the power transfer iscontinuously maximized when the relative positions of the transducersare altered due to breathing, body motion, or other causes.

As discussed above, the implantable receiver apparatus 740 includes areceiving transducer 742 (referred to as receiving transducer 642 inFIG. 6) (that receives the acoustic (e.g., ultrasonic) energytransmitted from the transmitting transducer 730 and converts it intoelectrical energy to charge a battery 744 or directly power an implantedmedical device. The battery 744 can be coupled to a rectifier (e.g., abridge rectifier, as discussed above). The transmitter apparatus 720 andimplantable receiver apparatus 740 can communicate via Bluetooth,another wireless communication device, or via ultrasound as discussedherein.

At an operating frequency of 1 MHz, the 3 mm square piezoelectricelements 731 are 2 wavelengths wide (4λ² area). This size was chosen toallow for the array to be steered by an angle of ±15 degrees without alarge loss of main lobe energy. The array will exhibit grating lobes,especially at larger steering angles, but this is not anticipated tosignificantly interfere with the intended operation.

This transmitter design allows for detailed control of the emittedfield, enabling a high level of system performance with a simplereceiver. In one embodiment, the receiver is a single piezo element. Inanother embodiment it may be an array. The receiver design is preferablykept within the volume budget of the apparatus to satisfy the clinicalrequirements of the product. Choice of the appropriate array parameterscan be facilitated by modeling of the transmitter beam forming and itsinteraction with the receiver. Modeling demonstrates an important point,the decreasing sensitivity to alignment of two plane parallel transducerfaces.

Maximum power transfer takes place when the incoming wave is at the samephase at all points on the receiver. In order to keep the incoming wavefrom the transmitter in phase across the face of the receiver, the twomust be aligned to within one-half wavelength, which for a frequency of1 MHz in tissue is approximately 1 mm. This alignment condition becomesmore and more stringent as the diameter of the transducers increases. Inan embodiment, for a 10 mm diameter transducer, the alignment conditionis that the two surfaces be parallel to 1 mm out of 10 mm. For a 70 mmdiameter transducer, the condition is 1 mm out of 70 mm. This conditionis relaxed for an array because the width of the array elementsubstitutes for the overall width of the whole array. An array elementwidth can vary from 0.1 mm to several millimeters in an exemplaryembodiment.

This relaxation is shown in FIG. 8 in an exemplary model-basedcalculation result 800 for an ultrasound frequency of 1 MHz and 25 mmdiameter transducers. Therein is plotted the steered power versus thenumber of array elements for a pair of 25 mm diameter transducers, wherethe transmitter is a one-dimensional array, and the receiver is amonolithic single element. The narrowest trace is for one element, andthen follow in increasing width the traces for 4, 7, and 10 elements.For a single 25 mm diameter transmitter element (the whole transducer),the power falls to 80% with one degree of misalignment on either side ofthe center line. Increasing the number of elements per unit area to 10spreads the 80% power cone to plus or minus 8 degrees (i.e., ±8°). Thatin turn, reduces the restriction on the angular alignment to retain 80%power to ±8° according to the foregoing exemplary embodiment.

As discussed above, a feedback loop can be provided between thetransmitter and receiver devices. The feedback loop can providenon-mechanical, hands-off alignment of the transmitter and receiverdevices.

Streaming orientation data from both sensors (e.g., accelerometer andmagnetometer) will be compared in real-time and used for rapidadjustment of the ultrasonic wavefront to maintain optimal alignment.The block diagram in FIGS. 1A and 7 shows how the transmitter andreceiver units are linked by a wireless feedback loop (e.g., Bluetooth).Alternatively, the feedback loop can be formed using the transmittedand/or received acoustic energy, as discussed below.

FIG. 9 is a flow chart 90 that illustrates an exemplary basic feedbackmethod used to optimize the position of each axis of the lateral andangular alignments, and the frequency from the signal generator. In step900, the angular or lateral position for each axis or frequency is sweptacross its entire range with a gross step between each position orfrequency, while measuring the level of the receiver power. Examples ofthe gross steps are: X-Y steps of ±2 mm; angular steps of ±2 degrees;and/or frequency steps of ±10 kHz. At each step the receiver power iscalculated by the product of the voltage and current going to thebattery, determined in the charging chip and relayed from the receiverunit to the controller, which then sets the next step. In step 910, analgorithm in the external controller determines where the highest poweris achieved in the multi-dimensional surface composed of all positionparameters plus the frequency. In step 920, the positions and frequencyare again swept but across a smaller range centered around the optimumparameters from the gross step sweeps in step 900, but at a smaller stepsize on the order of 25% of the gross steps. For example, the smallerstep size can include X-Y steps of ±0.5 mm; angular steps of ±0.5degrees; and/or frequency steps of ±2.5 kHz. The flow chart 90 thenreturns to step 910 to determine the optimum parameters for highestlevel of power received by the implantable receiver at the smaller stepsize. This process is repeated using progressively smaller step sizes(e.g., each iteration through step 920 can have a step size of 25% ofthe prior iteration) until at step 930 the statistical variation is lessthan a threshold value, such as is inside error bars or within apredetermined variance. In step 940 the electroacoustic impedance ismatched dynamically, by optimally coupling the matching layer betweentransducer and skin tissue.

Individual power measurements may vary due to electronic noise effects.With gross steps, it is easy to measure distinct changes, but as thestep size decreases, the noise floor quickly overcomes the differencesin power created by a change in position or frequency. To get a finerstep size and still be able to discern a clear change in power, anaveraging of ten measurements is useful. In another embodiment, theaveraged measurements can be filtered for each location and frequency.Similar fine alignment can be performed by optimizing the back reflectedacoustic signal from the receiver surface by using a short scout-pulseprior to operating the system to power transfer mode, as well asintermittently between the charging phases

In some aspects, the surface of the ultrasound transmitter can bedesigned such that a “dry application” on the skin tissue can beaccomplished, without the existing “wet gel” used for medical ultrasoundapplications. FIGS. 10A and 10B illustrate examples of a dry couplingmedium. FIG. 10A illustrates an example of an acoustic impedance-matchedboot coupling 1050 for a transducer 1020. FIG. 10B illustrates a sideview of a cross-section of a switchable transmitter transducer aperture1060 to optimize acoustic energy delivery to an implant using animpedance optimized dry coupling 1070, along with dynamic tissuecoupling feedback 1080 to external controller 100 to maximize acousticenergy delivery through tissue. The dry couplings 1050, 1070 may beuseful for efficiently delivering acoustic energy from the acousticsource into the tissue. The dry couplings 1050, 1070 can include apolyurethane-based, silicone based, natural oils, fatty-acid based,polyacrylamide-based, and/or hydrophilic gel-based materials. Otherembodiments may additionally or instead include attachment of apermanent or a single-use acoustic impedance-matched (e.g., acousticimpedance-matched boot coupling 1050) synthetic or natural polymer basedmaterial to the transducer surface. The material can include a hydrogel,a silicone-based material, natural oils, fatty-acid based, and/or apolyurethane. The dry couplings 1050, 1070 can have a known thickness,and can include one or more materials, each with a known thickness. Insome embodiments, the dry couplings 1050, 1070 have shape memory, andcan maintain its dimensions. A shape memory can assist in the layeradhering to a specific topology on the surface of a human. For dynamiccoupling, the controller within the transmitter apparatus constantlymonitors the level of electro-mechanical transmit impedance to match itfor optimal delivery of ultrasound energy into the tissue and throughthe dry coupling material. Transmit impedance also indicates to the userwhen the device is decoupled from the tissue surface. In someembodiments, dry couplings 1050, 1070 can be impregnated with lipophilicor hydrophilic material(s) that slowly is expressed between thetransducer and the skin tissue surface of the subject. In someembodiments, the dry couplings 1050, 1070 are formed of a material thatis temperature sensitive and changes in elasticity, density and soundspeed properties over the range 22° C.-38° C. In some embodiments, thedry couplings 1050, 1070 are designed to stand-off the normallyself-heating transducer face from skin. In some embodiments, thetransmitter and/or the external controller constantly (or periodically)monitors transducer impedance as well as back reflected signal from atissue layer or the implant to monitor a change of coupling parametersand to adjust the signal accordingly. In some embodiments, thetransmitter includes application specific switchable transmittertransducers. For example, the transmitter transducer can include anannular ring transducer, which can have more than one source diameterturned on at a given time.

In some aspects, the USer can use ultrasound as a means of communicationbetween the transmitting and receiving devices. Because ideal implantsrespond to physiological changes in the patient, the system implementsbidirectional communication between the charger and the implant forcontrol and monitoring. As discussed above, this communication can occurusing RF signals (e.g., Bluetooth). Alternatively, the acoustic energy(e.g., ultrasound), can be used as the carrier frequency for suchcommunication, which would eliminate the need for a RF antenna,simplifying the implant.

Specifically, it is realized that the transmitter can sense momentarychanges in the standing wave ratio, and those changes can be convertedto useful data exchange between transmitter and receiver. To produce alarge signal-to-noise ratio of the signal coming from the implant,especially at large depths, phase modulation is used instead ofamplitude or frequency modulation. Two-way communication is thusestablished without a transmitter in the implant.

FIG. 11 illustrates a schematic 1100 of two-way communication usingultrasound. The acoustic impedance of the receiving transducer 1142 inthe implantable receiver 1140 is modulated by modulating the electricalload attached to it in the form of the circuit 1144 that charges theimplant battery. As the charge current is momentarily increased 1146using a detection and charge modulation circuit 1148, the electricalload to the receiving transducer is increased and an acousticalimpedance change results. When the charge current returns to the nominalvalue the transducer impedance is restored. The change in receivingtransducer impedance is detected by the transmitting transducer on thetransmitter 1120 as backscattered amplitude-shifted keying datatransmission.

FIG. 12 is a flow chart 1200 of a method for providing power tobio-implanted medical device. The method in flow chart 1200 can beperformed with any of the devices described herein. In step 1210, anacoustic energy delivery device is secured on a subject's skin tissue,proximal to the bio-implanted medical device. In step 1220, acousticenergy is generated with a multi-dimensional array of transmittingelectroacoustical transducers on or in the acoustic energy deliverydevice. In step 1230, the acoustic energy is received with one or morereceiving electroacoustical transducers on or in a bio-implantedelectroacoustical energy converter that is electrically coupled to thebio-implanted medical device. In step 1240, the one or more receivingelectroacoustical transducers convert the acoustic energy intoelectrical energy. In step 1250, the converted electrical energy isprovided directly or indirectly to the bio-implanted medical device. Forexample, the converted electrical energy can be stored in a battery inthe bio-implanted medical device or in the bio-implantedelectroacoustical energy converter.

In the foregoing specification, the invention has been described withreference to specific embodiments. However, one of ordinary skill in theart appreciates that various modifications and changes can be madewithout departing from the scope of the disclosure and embodimentsdescribed herein. Accordingly, the specification and figures are to beregarded in an illustrative rather than a restrictive sense, and allsuch modifications are intended to be included within the scope of thisdisclosure.

What is claimed is:
 1. A system for providing energy to abio-implantable medical device, the system comprising: an acousticenergy delivery device configured to be secured to a patient's skin andapposed superficial tissue, the acoustic energy delivery devicecomprising: a delivery device housing; a multi-dimensional array oftransmitting electroacoustical transducers disposed on or in thedelivery device housing, the multi-dimensional array of transmittingelectroacoustical transducers arranged in a substantially regulartwo-dimensional geometric shape; a signal generator and power outputboard disposed in the delivery device housing, the signal generator inelectrical communication with the multi-dimensional array oftransmitting electroacoustical transducers; a microprocessor-basedcontroller disposed in the delivery device housing, themicroprocessor-based controller in electrical communication with thesignal generator and the multi-dimensional array of transmittingelectroacoustical transducers; and a battery disposed in the deliverydevice housing, the battery electrically coupled to themulti-dimensional array of transmitting electroacoustical transducers,the signal generator and power output board, and themicroprocessor-based controller; a bio-implantable electroacousticalenergy converter configured to be electrically coupled to thebio-implantable medical device, the bio-implantable electroacousticalenergy converter coupled to the patient's skin tissue comprising: aconverter device housing; one or more receiving electroacousticaltransducers disposed on or in the converter device housing, the one ormore receiving electroacoustical transducers configured to convertacoustic energy received from the acoustic energy delivery device intoconverted electrical energy; and an energy rectification and storagedevice disposed in the converter device housing, the energy storagedevice in electrical communication with the one or more receivingelectroacoustical transducers to store at least a portion of theconverted electrical energy.
 2. The system of claim 1, wherein thebio-implantable electroacoustical energy converter further comprises amicrocontroller disposed in the converter device housing.
 3. The systemof claim 2, further comprising a wireless feedback loop between thebio-implantable electroacoustical energy converter and the acousticenergy delivery device.
 4. The system of claim 3, wherein themicrocontroller is configured or programmed to modulate an impedance ofthe one or more receiving electroacoustical transducers to form thewireless feedback loop.
 5. The system of claim 4, wherein themicrocontroller is configured or programmed to modulate an electricalload on a charging circuit that electrically couples the one or morereceiving electroacoustical transducers to the energy storage device. 6.The system of claim 3, wherein the acoustic energy delivery devicefurther comprises a first RF antenna and the bio-implantableelectroacoustical energy converter further comprises a second RFantenna, the wireless feedback looped formed by RF communication betweenthe first and second RF antennas.
 7. The system of claim 1, furthercomprising a programmable external controller in electricalcommunication with the acoustic energy delivery device.
 8. The system ofclaim 1, wherein the microprocessor-based controller is configured orprogrammed to adjust a relative phase of input signals generated by thesignal generator to steer a beam of the ultrasonic energy.
 9. The systemof claim 1, further comprising first magnets disposed on the deliverydevice housing and second magnets disposed on the skin tissue or on theconverter device housing, the first magnets having an opposite polarityto the second magnets to magnetically retain an alignment of theacoustic energy delivery device and the bio-implantableelectroacoustical energy converter.
 10. The system of claim 1, furthercomprising both x-y-z and angular alignment mechanical devices tooptimize alignment of transmitter transducer and receiver transducerfaces.
 11. The system of claim 1, further comprising an acousticallytransparent adhesive to secure the acoustic energy delivery device tothe patient's skin.
 12. The system of claim 1, wherein the acousticenergy delivery device and the bio-implantable electroacoustical energyconverter each comprise a gyroscope and an accelerometer.
 13. The systemof claim 12, wherein the microprocessor-based controller receivesangular position and translational position data from the gyroscope andthe accelerometer in the acoustic energy delivery device and from thegyroscope and the accelerometer in the bio-implantable electroacousticalenergy converter, the microprocessor-based controller configured orprogrammed to adjust a relative phase of input signals generated by thesignal generator to steer a beam of the ultrasonic energy according to arelative angular position and a relative translational position of thebio-implantable electroacoustical energy converter with respect to theacoustic energy delivery device.
 14. The system of claim 1, furthercomprising a dry acoustic coupling between the multi-dimensional arrayof transmitting electroacoustical transducers and the patient's skin.15. The system of claim 14, wherein the dry acoustic coupling comprisespolyurethane, silicone, natural oils, fatty-acids, polyacrylamide, alipophilic material, or a hydrophilic material.
 16. The system of claim14, wherein the dry acoustic coupling includes a dynamic coupling tooptimize impedance matching of the transmitting electroacousticaltransducers to the dry coupling material.
 17. A method for providingpower to bio-implanted medical device, the method comprising: securingan acoustic energy delivery device on a subject's skin tissue proximalto the bio-implanted medical device; generating acoustic energy with amulti-dimensional array of transmitting electroacoustical transducers onor in the acoustic energy delivery device; receiving the acoustic energywith one or more receiving electroacoustical transducers on or in abio-implanted electroacoustical energy converter that is electricallycoupled to the bio-implanted medical device; with the one or morereceiving electroacoustical transducers, converting the acoustic energyinto electrical energy; and providing the electric energy to thebio-implanted medical device.
 18. The method of claim 17, furthercomprising providing a wireless feedback signal from the bio-implantedelectroacoustical energy converter to the acoustic energy deliverydevice, the wireless feedback signal corresponding to a magnitude of theacoustic energy received by the bio-implanted electroacoustical energyconverter.
 19. The method of claim 18, wherein the acoustic energydelivery device adjusts an angular or lateral position of a beam of theacoustic energy based on the wireless feedback signal.
 20. The method ofclaim 18, wherein the acoustic energy delivery device adjusts afrequency of the acoustic energy based on the wireless feedback signal.21. The method of claim 18, wherein the feedback signal is provided byvarying an acoustic impedance of the one or more receivingelectroacoustical transducers.
 22. The method of claim 18, furthercomprising adjusting a relative phase of input signals to themulti-dimensional array of transmitting electroacoustical transducers tosteer a beam of the acoustic energy based on the wireless feedbacksignal.